# This program is free software; you can redistribute it and/or modify it under
# the terms of the (LGPL) GNU Lesser General Public License as published by the
# Free Software Foundation; either version 3 of the License, or (at your
# option) any later version.
#
# This program is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
# FOR A PARTICULAR PURPOSE. See the GNU Library Lesser General Public License
# for more details at ( http://www.gnu.org/licenses/lgpl.html ).
#
# You should have received a copy of the GNU Lesser General Public License
# along with this program; if not, write to the Free Software Foundation, Inc.,
# 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
# written by: Jeff Ortel ( jortel@redhat.com )

"""
Provides XML I{special character} encoder classes.

"""

import re


class Encoder:
    """
    An XML special character encoder/decoder.

    @cvar encodings: A mapping of special characters encoding.
    @type encodings: [(str, str),...]
    @cvar decodings: A mapping of special characters decoding.
    @type decodings: [(str, str),...]
    @cvar special: A list of special characters.
    @type special: [char,...]

    """

    encodings = (
        ("&(?!(amp|lt|gt|quot|apos);)", "&amp;"),
        ("<", "&lt;"),
        (">", "&gt;"),
        ('"', "&quot;"),
        ("'", "&apos;"))
    decodings = (
        ("&lt;", "<"),
        ("&gt;", ">"),
        ("&quot;", '"'),
        ("&apos;", "'"),
        ("&amp;", "&"))
    special = ("&", "<", ">", '"', "'")

    def encode(self, s):
        """
        Encode special characters found in string I{s}.

        @param s: A string to encode.
        @type s: str
        @return: The encoded string.
        @rtype: str

        """
        if isinstance(s, basestring) and self.__needs_encoding(s):
            for x in self.encodings:
                s = re.sub(x[0], x[1], s)
        return s

    def decode(self, s):
        """
        Decode special characters encodings found in string I{s}.

        @param s: A string to decode.
        @type s: str
        @return: The decoded string.
        @rtype: str

        """
        if isinstance(s, basestring) and "&" in s:
            for x in self.decodings:
                s = s.replace(x[0], x[1])
        return s

    def __needs_encoding(self, s):
        """
        Get whether string I{s} contains special characters.

        @param s: A string to check.
        @type s: str
        @return: True if needs encoding.
        @rtype: boolean

        """
        if isinstance(s, basestring):
            for c in self.special:
                if c in s:
                    return True
